Oil and gas exploration, completion, and production operations often require the handling, transfer, and storage of large fluid volumes. Hydraulic fracturing techniques can require more than five million gallons of water per well. This large volume can be stored on site prior to and between fracturing operations, for storage, reuse and/or treatment and disposal. In addition, wells may produce large quantities of water during production. Due to environmental concerns, this water must be stored in a manner which will prevent contamination of the surrounding environment.
Often, large open pits are dug near the wells and used to store the water on or close to the well site. Environmental concerns are beginning to limit this practice. In addition to being unsightly, these pits can cause groundwater contamination, and are potential hazards to local livestock or wild animals long after drilling, completion, and production operations. Another option is the construction of steel tanks on site for storing fluid. The cost of construction, maintenance, and removal makes these options impractical in many cases.
As an alternative to pits and tanks, large fleets of tanker trucks, sometimes known as frac tanks have been employed to store fluid on a well site. Though these tanks can be redeployed from site to site recouping some of their cost more efficiently than built on site tanks, the enormous amount of resources necessary to move a fleet of tanks from site to site reduces the potential cost savings. Further, in environmentally sensitive areas, the movement of such large amounts of equipment may have serious consequences to roads and the local environment as well as create a disturbance to communities in which this equipment comes into contact.
A recent solution to the above problems has been the use of temporary tanks built on site for the storage of fluids. The problem with construction on site is that it can be costly and time consuming. A preferred method is to prepare a surface, erect a retaining wall of appropriate dimensions and then line the tank with a waterproof liner. The liner is heavy and difficult to install. Due to the thickness of the material used in the liner, it may take ten to twenty men and heavy equipment to maneuver the liner in place, and then lift the liner in small sections to secure it to the top of the wall.
Liners are large and bulky, and a full inspection can be extremely time consuming, if it can be accomplished at all. Due to the industrial environment and the large impact a small leak can have on the surroundings, it is often desirable to utilize more than one liner as a safety measure further increasing the effort and expense of erecting such a container. Liners are typically only used once and need to be disposed of after the tank is moved. This adds a significant cost to the storage operation and creates an additional waste stream. In the case that these tanks are used to store anything other than fresh water (such as produced or fracturing fluid flow back water), two or more liners are usually required, significantly increasing the overall cost of storage.